In the process of making printing plates, from the requirement of performing a contact exposure step (so-called contact work or duplicate work) using a relatively low speed light-sensitive material in a bright room, a photographic light-sensitive material which can be handled under an environment which can be considered a substantial bright room while using silver halide as the photosensitive element has been provided. This is attained by light-exposing a light-sensitive material having a reduced sensitivity to visible light under a safelight containing substantially no ultraviolet light, to a light source having wavelengths of less than 420 nm.
On the other hand, for the so-called contact work, not only a simple one sheet contact duplicate (i.e., a light-sensitive material for a duplicate is exposed in contact with one sheet of processed photographic film and developed to performed nega-posi image conversion) but also a high image conversion work, the so-called white lettering on a solid background, are performed. The term "white lettering on a solid background" means non-inked portions of letters, marks, etc., in the portions having ink dot-like on a paper (dot portions) and the portions having an ink overall on the paper (called solid black portions) in a print. More practically, a method of making white lettering on solid background in a photomechanical process is explained by referring to the accompanying drawing. That is, as shown in FIG. 1, a transparent or translucent film base 3 (usually, a polyethylene terephthalate film having a thickness of a few hundred .mu.m is used) having attached thereto a processed photographic film 4 with dot images (dot original) is superposed with a similar film base 1 having attached thereto a processed photographic film 2 having the so-called line positive images such as letters, marks, etc., formed thereon (line image original), the assembly as an original is superposed on a light-sensitive material 5 for duplication such that the dot image portion is in close contact with the surface of the silver halide emulsion layer of the light-sensitive material 5, and the light-sensitive material is exposed and processed to form white line image portions in the dot images. In the above-described process, it is important that dot images and line images perform nega/posi conversion in conformity with the dot area and the line width, respectively. For example, a dot image having a black area of 50% must be accurately converted into a white area of 50% and a line image having a back line width of 50 .mu.m into a white line width of 50 .mu.m.
However, as is clear by FIG. 1, the dot images are in direct contact with the emulsion surface of the light-sensitive material 3 for duplication on light exposure but the line images are exposed onto the light-sensitive material for duplication through the dot image original 4 (usually having a thickness of about 110 .mu.m) and the film base 3 (having a thickness of few hundreds .mu.m) for the dot images. That is, the line images are printed onto the light-sensitive material for duplication as blurred images through transparent or translucent spaces having few hundreds .mu.m thick. Thus, if an ordinary exposure amount (an exposure amount capable of faithfully performing the nega/posi conversion of dot images) is employed, the white line width of the line image is thinned due to the influence of the blurring exposure. On the other hand, if the exposure amount is decreased to reduce the influence of the blurring exposure to faithfully perform the nega/posi conversion of the line width of the line image, the dot area is thinned due to a lack of exposure. These phenomena are greatly influenced not only by the light-sensitive material but also by the light source for the light exposure. In other words, if the light source for exposure is small such as a point light source, the extent of the aforesaid blurring exposure is reduced. However, in the bright-room type light-sensitive material as used in this invention, an exposure device of a large light quality must be used and hence the light source is larger than that of a conventional bright room-type exposure device. This results in causing a deterioration of the quality of white lettering on solid background.
A means for preventing the occurence of such a deterioration of the white lettering on a solid background is described in JP-A-58-190943. (The term "JP-A" as used herein means an "unexamined published Japanese patent application"). However, in the case of using a light-sensitive material with a silver halide of the grain sizes described in the examples of the aforesaid JP-A application, there is the problem that the quality of white lettering on a solid background is reduced by scattering of light on the silver halide grains in the emulsion layer and hence a silver halide emulsion of fine grain sizes giving less scattering of light has been required.
Also, in order that a light-sensitive material can be allowed to stand for a long period of time under a safe fluorescent lamp, the content of silver bromide in the silver halide emulsion for the light-sensitive material must be reduced but since in such silver halide grains, the solubility is increased as the grain sizes thereof are reduced, a method of stably preparing such silver halide grains has not yet been found.
That is, since silver halide grains mainly composed of silver chloride grains having a mean grain size of less than 0.15 .mu.m have high solubility, the grain formation is performed by reducing the temperature for the grain formation or increasing the addition rates of the solutions of grain-forming components for reducing the grain sizes, but in this case, there is a problem that physical ripening proceeds during and/or after grain formation and in particular, the grain size is increased or the grain form is deformed in the desalting step (flocculation step or water washing step) and in the post-ripening step. Also, in the case of performing the grain formation at low temperature of lower than 30.degree. C, it is difficult to control the temperature at a constant temperature for the production of the silver halide grains and hence a method for stably producing such silver halide grains has been desired.
Furthermore, in silver halide grains mainly composed of fine grain silver chloride, the grain sizes are greatly changed after the formation of grains, in a desalting step, and/or in the post-ripening step. If a compound absorbing onto the surface of silver halide grains is added as a grain growth inhibitor for preventing a change in grain sizes, the change in the grain sizes can be reduced but there is a problem of changing the crystal habit. Thus, a method of preparing such silver halide without changing the grain sizes and the crystal habit has been desired.
On the other hand, since a grain growth inhibitor is generally a compound such as an antifoggant or a stabilizer, if the inhibitor remains in a silver halide emulsion after washing with water in the case of preparing the silver halide grains in the presence thereof, a problem that the inhibitor greatly inhibits the subsequent chemical ripening by the chemical sensitizer to reduce the photographic sensitivity and Dmax to an extent that such is unsuitable for practical use and a problem of a large obstruction of the adsorption of spectral sensitizing dye(s) on the silver halide grains occur. Thus, a method of solving these problems has been keenly desired.
Also, silver chloride grains having grain sizes of less than 0.15 .mu.m cause a problem that uneven development tends to occur at development. In particular, the occurence of uneven squeezing of rollers at the development section of an automatic processor is also a large problem. This is also considered to be caused, by the high solubility of the silver halide grains and this phenomenon severely occurs in the case of a fine grain silver chloride emulsion. Thus, a method of overcoming the difficulty has been very earnestly desired.
Also, when a primitive emulsion prepared is stored in a refrigerator for a long period of time (1 to 3 months), in silver halide grains having a mean grain size of less than 0.15 .mu.m and composed of more than 80 mol % silver chloride, the grain sizes are increased or grains are deformed resulting in serious problems in the stability of the primitive emulsion.
Furthermore, when a primitive emulsion is dissolved and is allowed to stand as a coating solution in the dissolved state for a long period of time (2 to 10 hours), serious problems that physical ripening occurs and the grain sizes are increased or grains are deformed changing the photographic properties.
As described above, silver halide grains having a mean grain size of less than 0.15 .mu.m and composed of more than 80 mol % silver chloride have the problems of increasing the grain sizes or changing the form of the grains due to the high solubility and hence a method of solving the problems has been keenly desired.
On the other hand, in the graphic arts field, for improving the reproduction of continuous tone images by dot images or the reproduction of line images, an image-forming system showing photographic characteristics of a super high contrast (in particular, a gamma higher than 10) is required. For the purpose, a specific developer called a lith developer has hitherto been used. A lith developer contains hydroquinone only as the developing agent, and in the lith developer, a sulfite as a precursor is used in the form of an addition product thereto with formaldehyde to greatly reduce the concentration of free sulfite ions (usually below 0.1 mol/liter) so as not to deteriorate the infectious development ability of the developer. Accordingly, there is a problem that the lith developer has a high tendency to be air-oxidized and can not be stored for over 3 days. Also, there is the disadvantage that the developing time is long. Thus, a quick and stable developing process has been keenly desired.
As a process of obtaining high contrast photographic characteristics using a stable developer, processes of using hydrazine derivatives are described in U.S. Pat. Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606, 4,221,857, 4,269,929, and 4,650,746. According to the aforesaid processes, photographic characteristics of super high contrast and high sensitivity are obtained and further the stability of the developer to air oxidation is greatly improved as compared to a lith developer since a sulfite can be added at a high concentration to the developer.
However, although the aforesaid image-formig system is suitable for a high contrast system of a very high sensitivity, it is difficult to obtain a low speed light-sensitive material for a bright room, which is widely used for contact work in a printing plate making process.
A method of obtaining a low speed light-sensitive material containing hydrazine for bright room is disclosed in JP-A-60-162246 and JP-A-61-238049. In these known systems, the amount of rhodium added is less and they are insufficient in reducing the sensitivity. JP-A-60-14038 discloses a system containing a large amount of rhodium but the tone obtained in such a system is very soft. Also, Japanese Patent Application No. 62-65116 describes a silver halide photographic material providing high contrast characteristics using hydrazine having an adsorptive group for the silver halide containing more than 1.times.10.sup.-5 mol of a rhodium salt, but the light-sensitive material is still insufficient in terms of the quality of white lettering on a solid background, which is important for performance as a light-sensitive material for duplication. Also, an image-forming process of processing a light-sensitive material with a developer containing substantially hydroxybenzene only as the developing agent and a large amount of sulfite is disclosed in U.S. Pat. No. 4,452,882 and JP-A-54-37732, JP-A-60-97348 and JP-A-61-47951.